1. Field of the Invention
The present invention relates generally to a screw anchor which may be installed in the earth by means of a rotational driving force for use in supporting loads. More particularly, the invention hereof concerns a clamshell screw anchor having a combined hub and earth-engaging lead point formed from a substantially flat piece of material folded about a line of symmetry. In another embodiment, a pair of substantially identical, flat pieces of material are formed and coupled to present a combined hub and earth-engaging lead point.
2. Description of the Prior Art
Presently, in the field of screw anchors, it is known to provide a screw anchor device including an anchor member coupled with an elongated rod component. For example, U.S. Pat. No. 4,334,392, issued to Dziedzic, discloses a screw anchor including an anchor member, and an earth-engaging lead point. The anchor member includes a hollow, round-cornered square hub, and a helical load bearing element that is secured around the hub. The earth-engaging lead point is either formed integrally, or threadably coupled, with a rod component and is received through and operably coupled with the hub so that when the assembly is installed in the ground, tension forces may be effectively resisted by the helical load-bearing element.
In operation, the hub and lead point are engaged by a wrench of a source of rotational driving force, and the anchor is rotatably driven into the earth. Once driven into the earth, the rod is attached to a guy wire. The guy wire, in turn, is used to support devices, such as electric transmission poles, or other similar structures. The rod and lead point component, however, are not securely attached to the anchor. As a result, the screw anchor disclosed in the '392 patent is relatively difficult to handle.
U.S. Pat. No. 4,467,575, issued to Dziedzic, discloses another screw anchor device based on the device disclosed in the '392 patent. The anchor disclosed in the '575 patent includes improvements in the design and construction of the anchor member. For example, a twist-lock feature is provided to couple the rod and lead point to the anchor so that the resulting assembly can be handled as one piece. This device also includes an improved earth-penetrating lead point, facilitating installation in rocky and frozen earth.
These prior art devices, however, are relatively expensive to manufacture. For example, these devices require lead point elements which are either cast or hot-forged into shape. Such operations are labor intensive and time consuming, making them relatively expensive and subject to production delays.
A unitary cast screw anchor is disclosed in U.S. Pat. No. 4,981,000, issued to Hamilton et al. This device is relatively strong so that it may be driven into rocky and frozen soils. The unitary cast construction, however, renders it relatively expensive, and subject to production delays. Therefore, a significant and heretofore unsolved need exists to provide a screw anchor which is relatively inexpensive and easy to manufacture.